water quality

A question for people who are doing studies with RNA like RT-PCR and in
situ hybridization for RNA:
what sort of water do you use?
a) regular distilled water that is treated with DEPC and then autoclaved
or
b) ultrapure water (f.ex. MilliQ)that is treated with DEPC and then
autoclaved
one of my collegues says that there is no need for ultrapure water, but I
would like to have some more opinions before I cut down my standards. (In
the lab where I was trained in molecular biology everything (also non-RNA
buffers etc) was prepared with ultrapure water.
thanks for some arguments
Dr. Heike Grabsch, Germany